1. Field of the Invention
The present invention relates to a method for correcting alignment to make a relative alignment between patterns in a plane direction for forming a plurality of patterns in manufacturing a semiconductor device, a method for manufacturing a semiconductor device and a semiconductor device.
2. Description of the Background Art
Now discussion will be presented on alignment with reference to a conceptional diagram of FIG. 24. A plane 3a has patterns la and alignment marks 2a to 2d. A plane 3b has patterns 1b and alignment marks 2e to 2h. The patterns 1a and 1b are formed on wafers and made of silicon compound, metal or the like. The alignment marks 2a to 2d are formed simultaneously with the patterns 1a. The alignment marks 2e to 2h are formed simultaneously with the patterns 1b. An operation to relatively align positions of two objects, such as the planes 3a and 3b, is referred to just as xe2x80x9cAlignmentxe2x80x9d.
In a process for manufacturing a semiconductor device, several major steps are performed to manufacture the semiconductor device. The major step is a unit of a plurality of steps for forming a pattern (e.g., a film-formation step for forming a film on a wafer, a resist coating step for coating a resist, an exposure step, a developing step, an etching step for patterning a film and so on).
FIG. 25 is a conceptional section of a semiconductor device. The semiconductor device of FIG. 25 is obtained through seven major steps, and patterns 301 to 307 are formed through the seven major steps, respectively.
The alignment is required in the exposure step. In the exposure step, actually, an alignment is performed to relatively align the positions of a reticle and a wafer. Among apparatuses for exposure and alignment is a step-type projection aligner (hereinafter, referred to as xe2x80x9cstepperxe2x80x9d).
FIG. 26 is a block diagram of a manufacturing system 10 for manufacturing a semiconductor device. This figure shows steppers 4 as mentioned above, overlay checking devices 5, a production control system body 6 for performing a production control which includes an alignment correction unit 6a and a database 6b, semiconductor manufacturing devices 7 and reference terminals 8 connected to the production control system body 6 for making reference to the database 6b. In this system, there are a plurality of steppers 4 and semiconductor manufacturing devices such as a sputtering device and an etching device.
Among patterns which are aligned by the stepper 4, there exist a shear despite of the alignment. This is due to a mechanical error of the stepper, a manufacture error of the reticle and so on. The stepper 4 is given a correction value for resolving the shear (hereinafter, referred to as xe2x80x9cstepper correction valuexe2x80x9d). On the other hand, the overlay checking device 5 detects the shear and calculates a correction value for resolving the shear (hereinafter, referred to as xe2x80x9cOCCV (overlay checking correction value)xe2x80x9d).
The production control system body 6 controls data on alignment (hereinafter, referred to as xe2x80x9calignment dataxe2x80x9d). The alignment data include the OCCV, the step correction value, the type of wafer (lot No., product No. and the like), date of alignment, processing, production history and so on. The alignment data are stored in the database 6b. 
The alignment correction unit 6a is one of functions of the production control system body 6 and calculates the stepper correction value.
FIG. 27 illustrates a constitutional conception of the stepper 4. In this figure shown are a wafer stage WST on which a wafer 20 is mounted, a reticle stage RST on which a reticle 30 is mounted, an illumination system ILS, a lens system PL, a stepper correction value for wafer component 22 and a stepper correction value for shot component 33.
The stepper 4 receives the stepper correction value. The stepper correction value includes the stepper correction value for wafer component 22 and the stepper correction value for shot component 33.
The stepper correction value for wafer component 22 is a value which is set to move the wafer. The stepper correction values for wafer component 22 includes stepper correction values for offsets X and Y (base line), scalings X and Y, X-Y orthogonality and wafer rotation. The wafer stage WST travels in accordance with the stepper correction values for wafer component 22.
The stepper correction value for shot component 33 is a value which is set to change an image 34 projected on the wafer 20 from the illumination system ILS through the reticle 30. The stepper correction values for shot component 33 include stepper correction values for shot rotation, magnification and the like. The image 34 varies with the stepper correction values for shot component 33. In more detail, as to the shot rotation, the reticle stage RST rotates about a center axis 32 to rotate the image 34. As to the magnification, the image 34 is enlarged or reduced by the lens system PL and the like.
The production control system body 6 processes the wafer as follows. Herein, an alignment of the plane 304 of FIG. 25 will be taken as an example. The processing is performed according to a flowchart of FIG. 28.
First, the production control system body 6 transports a wafer to be processed to the stepper 4. When the wafer reaches the stepper 4, the alignment correction unit 6a calculates the stepper correction value (Step S901 of FIG. 28).
The production control system body 6 sets the stepper correction value obtained by calculation to the stepper 4 (Step S902).
The stepper 4 performs an alignment (Step S903).
After completing the alignment, the production control system body 6 registers the stepper correction value in the database 6b to control the stepper correction value. Further, the wafer is transported from the stepper 4 to the overlay checking device 5 (Step S904),
The overlay checking device 5 detects a shear between the pattern 304 and the pattern 303 immediately therebelow with the positions of the alignment marks (Step S905). Further, the device 5 calculates the OCCV to resolve the detected shear (Step S906).
Subsequently, the production control system body 6 collects the OCCVs from the overlay checking devices 5 (Step S907). The system body 6 stores the collected OCCVs in the database 6b and controls them (Step S908).
Further, the production control system body 6 transports the wafer to be processed to the semiconductor manufacturing device 7, as needed, where sputtering, etching and the like are performed.
Through the above steps, the production control system body 6 processes the wafer.
Next, a method for correcting alignment to calculate the stepper correction value in the background art will be discussed with reference to FIGS. 29 and 30. It is assumed that the stepper correction value set in the Step S902 is +1 and the OCCV (which herein corresponds to the shear) detected in the Step S906 is xe2x88x922 in this alignment performed in the major step. Therefore, as shown in FIG. 30, if the stepper correction value is set at +3 in the alignment of the next major step, it is expected that the OCCV should be 0. The calculated difference between the stepper correction value and the OCCV is referred to as xe2x80x9ctrue shearxe2x80x9d. Specifically, this is expressed as,
true shear=stepper correction valuexe2x88x92OCCVxe2x80x83xe2x80x83(1)
Shorter time lag between the present alignment and the next alignment causes smaller true shear.
As the time lag becomes longer, the true shear becomes larger. Then, the production control system body 6 controls a trend of the true shear in a major step as shown in FIG. 31, and the alignment correction unit 6a calculates a mean value of true shears at the time points P1 to P3 in the same major step as the stepper correction value to be set in the next major step tx.
Thus, in the background-art method for correcting alignment, the stepper correction value for wafer component is corrected to align a pattern with a pattern immediately therebelow, like the patterns 304 and 303.
For size reduction of a semiconductor device, a small tolerance (specification) of the shear between patterns is required. In recent, as the size of a semiconductor device becomes smaller, too much smaller tolerance has been established than ever. The shear between patterns used to be within specification if the stepper correction value for wafer component was corrected. With establishment of too much smaller tolerance, however, there recently arises a problem that some shear out of specification is caused when the background-art method for correcting alignment is performed, and an improvement in precision of alignment is required.
The present invention is directed to a method for correcting alignment used in a manufacturing system for manufacturing a semiconductor device including steppers to which stepper correction values are set to determine a position of a pattern to be aligned, by which the manufacturing system generates the stepper correction values. In the method, the manufacturing system manages in advance a lower pattern corresponding to the pattern to be aligned among a plurality of patterns in the semiconductor device. According to a first aspect of the present invention, the method comprises the steps of: (a) controlling the travel from a reference position to a position of the pattern to be aligned among the plurality of patterns in the semiconductor device by the manufacturing system; and (b) generating a value including the travel of the lower pattern corresponding to the pattern to be aligned as one of the stepper correction values to determine the position of the pattern by the manufacturing system.
According to a second aspect of the present invention, in the method of the first aspect, the stepper correction values in the step (b) represent shot components.
According to a third aspect of the present invention, in the method of the first aspect, the reference position is a position of the pattern at the time when the stepper correction values are zero.
According to a fourth aspect of the present invention, in the method of the third aspect further comprises the steps of: (c) detecting a shear between the pattern and the lower pattern corresponding thereto by a overlay checking device; and (d) adding the travel of a lower pattern corresponding to the lower pattern in the step (c) to the shear detected in the step (c) to obtain the travel of the lower pattern in the step (b).
According to a fifth aspect of the present invention, in the method of the first aspect, the manufacturing system manages in advance the reference position.
According to a sixth aspect of the present invention, in the method of the fifth aspect, the reference position is controlled by using reference stepper correction values, the reference stepper correction values are the stepper correction values set to the steppers to determine the reference position, and the method further comprises the step of: (c) subtracting the reference stepper correction values for the lower pattern from the stepper correction values set to determine a position of the lower pattern to obtain the travel of the lower pattern in the step (b).
According to a seventh aspect of the present invention, in the method of the first aspect, the stepper correction values include a stepper correction value for offset and a stepper correction value for shot rotation, the one of the stepper correction values generated in the step (b) is the stepper correction value for shot rotation, and the method further comprises the step of: (c) generating the stepper correction value for offset, and in the method, the travel is transformed into a variation of the stepper correction value for offset and the variation is added to the stepper correction value for offset in the step (c).
According to an eighth aspect of the present invention, the method of the first aspect further comprises the steps of: (c) comparing the stepper correction value with a predetermined threshold value; and (d) adding a value for reducing the stepper correction value to each of the stepper correction values when the each of the stepper correction values is not less than the threshold value as a result of the step (c).
The present invention is also directed to a method for manufacturing a semiconductor device. According to a ninth aspect of the present invention, the method comprises the step of positioning a pattern to be aligned by using the method for correcting alignment of the first to eighth aspects.
The present invention is further directed to a semiconductor device comprising a pattern aligned by using a method for correcting alignment, and the method for correcting alignment is used in a manufacturing system for manufacturing a semiconductor device including steppers to which stepper correction values are set to determine a position of a pattern to be aligned, by which the manufacturing system generates the stepper correction values. In the semiconductor device, the manufacturing system manages in advance a lower pattern corresponding to the pattern to be aligned among a plurality of patterns in the semiconductor device. According to a tenth aspect of the present invention, the method comprises the steps of: (a) controlling the travel from a reference position to a position of the pattern to be aligned among said plurality of patterns in the semiconductor device by the manufacturing system; and (b) generating a value including the travel of the lower pattern corresponding to the pattern to be aligned as one of the stepper correction values to determine the position of the pattern by the manufacturing system.
In the method of the first aspect of the present invention, by controlling the lower pattern and the travel of the lower pattern, it is possible to generate the stepper correction values including the travel of the lower pattern to determine the position of the upper pattern to be aligned. Therefore, the method produces an effect of preventing any shear out of specification between the upper and lower patterns.
Since the shot components are generally more likely to cause a shear than the wafer components, applying the method of the second aspect of the present invention produces an effect of preventing any shear out of specification between the upper and lower patterns.
In the method of the third aspect of the present invention, since the reference position for travel is the position of the pattern at the time when the stepper correction values are zero, the stepper correction values can be easily calculated.
The method of the fourth aspect of the present invention produces an effect of obtaining the travel by calculation using the shear detected by the overlay checking device.
In the method of the fifth aspect of the present invention, when the reference position controlled in advance is a position of the pattern at an initial state, the travel is the variation from the time point of initial state. Therefore, the relatively-positional relation between the pattern to be aligned and the lower pattern is made equivalent to the relatively-positional relation at the initial state.
The method of the sixth aspect of the present invention produces an effect of obtaining the self-variation by subtracting the stepper correction values for the lower pattern at the initial state from the stepper correction values set to determine the position of the lower pattern.
The method of the seventh aspect of the present invention produces an effect of preventing any offset out of specification.
By the method of the eighth aspect of the present invention, the stepper correction value over the threshold value is reduced. Therefore, the method produces an effect of preventing out-of-specification caused by abruptly setting a large stepper correction value.
The method of the ninth aspect of the present invention produces an effect of providing a semiconductor device having patterns which are positioned with high precision.
The method of the tenth aspect of the present invention produces an effect of providing a semiconductor device having patterns which are positioned with high precision.
An object of the present invention is to provide a method for correcting alignment which prevents any shear out of specification, a method for manufacturing a semiconductor device and a semiconductor device.
These and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.